Mechanical seals typically comprise a rotating component which is secured to a rotatable shaft and a stationary component which is secured to a housing. The interface between the seal faces of the rotating component and stationary component prevents the processed product from escaping.
Unfortunately, heat is generated at the interface between the seal faces of the rotating and stationary components due to the rotating action of the rotary component against the stationary component. It is essential that the heat is removed from the seal faces because it may lead to excessive wearing of the seal faces, lead to unwanted leakage between the seal faces and may even cause the mechanical seal to fail prematurely. The problem of unwanted heated is usually overcome by providing a film of fluid between the seal faces so as to lubricate and cool the components.
Seal support systems are commonly used to provide a mechanical seal with the requisite lubricating and cooling fluid. Seal support systems typically comprise a vessel or tank, which contains a volume of fluid. The vessel is piped to a mechanical seal on a pump, mixer or item of rotating equipment in order to provide fluid within the mechanical seal and particularly to form a film of fluid between the seal faces. A return pipe is arranged to lead fluid back to the vessel from the mechanical seal, hence closing the “loop”. This allows fluid repeatedly to enter and exit the mechanical seal, via the vessel. Such fluid is generally chosen so that it lubricates and cools the components within the mechanical seal, whilst being compatible with the process fluid.
The industry term of the fluid contained in the vessel and used to lubricate and cool the mechanical seal is “barrier” or “buffer” fluid.
As indicated above, seal support systems are well known and very effective in maintaining barrier fluid within a mechanical seal. One such system is described in UK Patent 2381838.
It has been found that it is difficult to ensure the vessel of a seal support system, and therefore the mechanical seal, remains sterile during use. Due to the closed loop arrangement the barrier fluid is recycled rather than discharged as waste immediately after cooling the mechanical seal. Hence, the barrier fluid is at risk of becoming stagnant within the vessel and/or contaminated and this may lead to the growth of pathogens such as bacteria, viruses and/or fungi. There are certain industries in which the sterility of machinery is essential, for example in the food, beverage or pharmaceutical industry. Accordingly, these industries are unable to use conventional seal support systems to maintain barrier fluid within a mechanical seal.
This problem has been overcome in the past by providing a seal support system with a manually operated discharge or flushing means. These typically include an outlet pipe from the vessel with a manually operated valve. The valve must be manually opened by a maintenance engineer once a day or as often as required in order to drain the vessel of barrier fluid.
However, the problem with such discharge means is that it is entirely reliant on manual operation. Hence, there is a risk that the seal support system is not sufficiently drained in order to avoid the stagnation of barrier fluid and ensure the barrier fluid remains pathogen and/or contaminate free. For example, the vessel may not be drained of barrier fluid as frequently as required. Nor may the vessel be drained for an appropriate period of time to ensure enough barrier fluid has been discharged. Alternatively, too much barrier fluid may be drained from the vessel leading to unnecessary wastage.